Heretofore, an actinic radiation curable composition which is cured with an active energy radiation such as a ultraviolet ray and an electron beam, is put in practical use of various applications, such as coating materials (for a plastic, a paper, a woodwork and an inorganic material), an adhesive agent, a printing ink, a print circuit board and an electric insulation.
And as an inkjet ink system which uses these polymerizable compositions, an ultraviolet ray curable inkjet ink which is hardened by an ultraviolet ray is well known. The inkjet recording method using the ultraviolet ray curable ink has been attracting attention in recent years from the point that it dries quickly and it can perform recording to a recording material having no ink absorptivity.
However, with the image forming method which uses an ultraviolet ray curable inkjet ink system, coalescence of adjacent dots which may be a problem during high-speed printing (for example, with a transportation speed of a recording material in the range of 30 m/s or more by using a line recording method, or with a printing speed of 50 m2/hour by using a serial (shuttle) recording method) cannot be fully inhibited. As a result, deterioration of an image causes.
Further, hot-melt ink system which uses 20% or more of phase changeable compound such as wax in ink composition has been attracting attention from the point that it can perform recording to a plain paper having no special treatment or a recording material having no ink absorptivity. However, it has problems that an image formed layer is easily peeled by nail.
Then, in order to solve these problems, radiation curable ink having gelling agent is disclosed (Patent Documents 1 and 2).
On the other hand, it is known that ink is circulated through ink flow path in order to avoid deterioration of an ejection property from inkjet recording head due to bubble in an ink (Patent Document 3).
However, by just print recording an actinic radiation curable ink containing gelling agent with conventional inkjet recording head, it is hard to form a high-resolution image as well as having high curability, because ink cannot be thoroughly gelled after landing onto recording medium resulting in unprinted portions such as hollow defect caused by coalescence of adjacent dots.
Prior Technical Document
Patent Document
Patent Document 1: Unexamined Japanese Patent Application Publication (hereinafter referred to as JP-A) No. 2006-193745
Patent Document 2: Japanese Translation of PCT International Application Publication No. 2009-510184
Patent Document 3: Japanese Translation of PCT International Application Publication No. 2008-513245